Power Electronics Europe April/May Issue 2022

www.microchip.com/en-us/product/MOSFET-SIC-1700V SILICON CARBIDE 21 www.power-mag.com Issue 2 2022 Power Electronics Europe others), which can be eliminated by using digital gate drivers to adjust the MOSFET’s turn-on parameters. Utilizing 1200V MSCSM120AM042CD3AG SiC MOSFET and AgileSwitch® 2ASC- 12A1HP digital gate driver, a jointly with French Mersen designed high-performance stack reference design allows to rapidly develop high-voltage systems using kits predesigned for typical and individual applications, reducing time to market by up to six months. This reference design provides 16 kilowatts per liter (kW/l) of power density, up to 130°C Tj and peak efficiency at 98 % with up to 20 kHz switching frequency. Looking to the future The ability to configure a digital gate driver creates new opportunities to change switching profiles in the field as MOSFETs degrade. This can already be done on a periodic basis – such as after a month or year of deployment. But there is no reason why it could not also be done dynamically, in real time, by sending a command to a controller that instructs the gate driver to change its settings. In the meantime, combining SiC power modules with digital gate drivers is enabling designers to quickly and easily influence critical dynamic issues including voltage overshoot, switching losses and EMI. The most granular turn-on/turn-off configuration options reduce or even eliminate the secondary effects of operating SiC switches. Packaged into total system solutions, these digital gate drivers are paving the way for significantly smaller auxiliary power units in metro, subway, and other heavy transportation vehicles that make room for more paying passengers. They also greatly accelerate time to market by eliminating months of system development time, transforming the design experience from soldering resistors onto a board to simply entering keystrokes to change gate driver behavioral parameters. Figure 3: The digital gate driver design example on the right shows an SP6LI low- inductance power module with connections to a laptop computer and a phase leg. Testing can begin immediately, without the laborious process of soldering gate resistors onto a board, shown on the left 3.3 kV SiC MOSFETs and Schottky Barrier Diodes (SBDs) extend designers’ options for high-voltage power electronics in transportation, energy and industrial systems Microchip’s new 3.3 kV SiC power devices, lauched at APEC 2022, include MOSFETs with lowest on-resistance of 25 m and Schottky Barrier Diodes (SBDs) with high current rating of 90 A. Both MOSFETs and SBDs are available in die or package form. Many Silicon- based designs have reached their limits in efficiency improvements, system cost reduction and application innovation. While high-voltage SiC provides a proven alternative to achieve these results, until now, the availability of 3.3 kV SiC power devices was limited. Microchip’s 3.3 kV MOSFETs and SBDs join the company’s comprehensive portfolio of SiC solutions that include 700 V, 1200 V and 1700 V die, discretes, modules and digital gate drivers. Customers can combine Microchip SiC products with the company’s other devices including 8-, 16- and 32-bit microcontrollers (MCUs), power management devices, analog sensors, touch and gesture controllers and wireless connectivity solutions to create complete system solutions at a lower overall system cost. To the question, if an internal body diode is suitable for replacing an external diode and save space in a power module, SiC manager Rob Weber commented: ”In general, yes, because of the reliable body diode of our devices, you may not need to use an external Schottky diode. However, it depends on details of the design. The Schottky diode has a lower forward voltage in most conditions and lower reverse recovery, resulting in overall lower losses. If there is enough margin in the thermal design then the body diode may be sufficient.” Adding an SBD in parallel with the MOSFET reduces power dissipation in most cases due to the lower forward voltage (V f ) of the Schottky. The positive temperature coefficient of the SBD at higher current (increasing V f with temperature) and the negative temperature coefficient of the MOSFET’s body diode means that at high temperature and high current, the body diode and SBD will share current. Therefore the first order improvement in power dissipation may not be realized due to this current sharing and higher V f of the SBD at high temperature. The MOSFET gate turn-off voltage is recommended to be -5 V to prevent the MOSFET’s channel from partially turning on during reverse current flow. A lower negative turn-off voltage would lead to increases current sharing between the SBD and MOSFET and negate the benefit of the Schottky diode. A 1:1 ratio of MOSFET to SBD is usually not required. In most cases, we use a 2:1 ratio of MOSFET to SBD, which saves on cost and area. The expanded SiC portfolio is supported by a range of SiC SPICE models compatible with Microchip’s MPLAB ® Mindi™ analog simulator modules and driver board reference designs. The Intelligent Configuration Tool (ICT) enables designers to model efficient SiC gate driver settings for Microchip’s AgileSwitch ® family of configurable digital gate drivers. Microchip Enters 3.3 kV SiC Power Market